1. Field of the Invention
The present invention relates to a changeover valve and a gas transportation pipe system for grain to which the changeover valve is applied. The changeover valve is particularly appropriate to be used for a pipe system for transporting grain such as rice and other granular material by introducing compressed air into pipes.
2. Description of Related Art
Conventionally, in rice polishing factories and boiled rice factories, transportation apparatuses such as bucket conveyers, lifts, horizontal belt conveyers and the like are usually used for transporting delivered rice, which is granular material, among equipment.
However, buckets, belts, driving motors and so on are required when the above-mentioned transportation apparatuses are used, which results in upsizing of the transportation apparatuses and brings about great difficulty in assembly and installation thereof. Furthermore, since rice bran remains in gap parts of the conveyors in the transportation apparatuses, microbes such as mold may grow to gather insects and so on eating the mold. This brings about a problem that values of rice and boiled rice as products may possibly be lost. Since the transportation apparatuses need to be frequently disassembled for cleaning in order to eliminate the problem, a problem is further caused that maintenance cost is increased.
As methods to solve these problems, methods of transporting rice with the use of air are known as are disclosed in Japanese Patent Laid-open No. Hei 7-330151, Japanese Patent Laid-open No. Hei 2-56255, and Japanese Patent Laid-open No. Sho 52-20582. In these methods, rice is transported by air streams which are generated in pipes by blowers and compressors. The use of such pneumatic transportation methods makes it possible to avoid the problem that the rice bran remains halfway in the pipes since the rice and the air are transported in the pipes which are shielded from the outside. FIG. 11 is a sectional view of a part on an end side of a gas transportation pipe system in a conventional transportation apparatus 1 for rice.
As is shown in FIG. 11, in the end side part of the transportation apparatus 1 which utilizes an air stream, a plurality of storage tanks 3 are installed below a pneumatic transportation pipe 2 and each of changeover valves 5 enables rice 4 which is transported through the pneumatic transportation pipe 2 to be accommodated in a specific one of the storage tanks 3.
Each of the changeover valves 5 is composed of a casing 6 and a valve disc 7 which is rotatably accommodated in the casing 6, and a lead-out angle to the storage tank 3 relative to the pneumatic transportation pipe 2 is set at a small value as shown in FIG. 11. This prevents the rice 4 transferred at a high speed from being crushed even when the rice 4 collides with inner walls of the changeover valves 5 since a collision angle is small.
However, the above conventional changeover valve 5 has a problem as described below.
FIGS. 12 to 14 are sectional views of the conventional changeover valve 5, FIG. 12 being a sectional view of the changeover valve 5, FIG. 13 being an enlarged view of the part D in FIG. 12, and FIG. 14 being an enlarged view of the part E in FIG. 12.
As is shown in these drawings, the conventional changeover valve 5 is composed of the casing 6 and the valve disc 7, and the rotation of the valve disc 7 causes an introducing passage 8 and a discharge passage 9a or 9b which are formed in the casing 6 to be connected to a through passage 10 which is formed in the valve disc 7 to pass the rice 4 therethrough. However, the casing 6 and the valve, disc 7 are separate bodies so that differences in inside diameters between the introducing passage 8 and the through passage 10 and between the discharge passage 9a or 9b and the through passage 10 may be sometimes caused through mechanical processes and the rice 4 may possibly be crushed when it collides with stepped parts, which are designated by the sizes t1 and t2, as shown in FIG. 12 and FIG. 13.
It is an object of the present invention to eliminate these problems and to provide a changeover valve which is capable of preventing granular material from being crushed when the granular material is transported by gas through a pipe system, and more particularly, a changeover valve which is capable of preventing grain such as rice from being crushed, cracked, broken, and chipped when grain such as rice is transported by gas through the pipe system. It is another object of the present invention to provide a gas transportation pipe system for grain such as rice to which the changeover valve is applied.
A changeover valve according to the present invention is a changeover valve comprising: a valve disc in a cylinder shape including on a side part thereof a through passage which is connected to transportation passages on an upstream side and a downstream side and which is in an eccentric position deviated from a center of the cylinder; a casing for rotatably accommodating the valve disc therein; and a pair of discharge passages which are provided in the casing and connected to the through passage of the valve disc,
wherein an inside diameter of an introducing passage of the changeover valve at an output end thereof is smaller than an inside diameter of the through passage of the valve disc and an inside diameter of the introducing passage in an output side part has a shape gradually decreasing in size toward the downstream side while an inside diameter of each of the pair of the discharge passages at an input end thereof is larger than the inside diameter of the through passage of the valve disc and an inside diameter of each of the pair of the discharge passages in an input side part has a shape gradually increasing in size toward the upstream side. It is also appropriate that the shape of the inside diameter of the introducing passage in the output side part thereof, which is gradually decreasing in size toward the downstream side, is a slope. It is also appropriate that the shape of the inside diameter of each of the pair of the discharge passages in the input side part thereof, which is increasing in size toward the upstream side, is in an arc shape.
Another changeover valve for a gas transportation pipe system for grain according to the present invention is a changeover valve comprising: a valve disc in a cylinder shape including on a side part thereof a through passage which is connected to transportation passages on an upstream side and a downstream side and which is in an eccentric position deviated from a center of the cylinder; a casing for rotatably accommodating the valve disc therein; and a pair of discharge passages which are provided in the casing and connected to the through passage of the valve disc,
wherein an inside diameter of an introducing passage of the changeover valve at an output end thereof is smaller than an inside diameter of the through passage of the valve disc and a diameter-reducing slope is formed in an output side part of the introducing passage with an inclination angle thereof equal to 30 degrees or less while an inside diameter of each of the pair of the discharge passages at an input end thereof is larger than the inside diameter of the through passage of the valve disc and an inside diameter of each of the pair of the discharge passages in an input side part has a shape gradually increasing in size toward the upstream side. It is also appropriate that the shape of the inside diameter of each of the discharge passages in the input side part thereof, which is increasing in size toward the upstream side, is in an arc shape.
A gas transportation pipe system for grain according to the present invention comprises a changeover valve comprising: a valve disc in a cylinder shape including on a side part thereof a through passage which is connected to transportation passages on an upstream side and a downstream side and which is in an eccentric position deviated from a center of the cylinder; a casing for rotatably accommodating the valve disc therein; and a pair of discharge passages which are provided in the casing and connected to the through passage of the valve disc,
wherein the changeover valve is structured in a manner in which an inside diameter of an introducing passage of the changeover valve at an output end thereof is smaller than an inside diameter of the through passage of the valve disc and an inside diameter of the introducing passage in an output side part has a shape gradually decreasing in size toward the downstream side while an inside diameter of each of the pair of the discharge passages at an input end thereof is larger than the inside diameter of the through passage of the valve disc and an inside diameter of each of the pair of the discharge passages in an input side part has a shape gradually increasing in size toward the upstream side and an angle made by center axes of the pair of the discharge passages is set at a value equal to 30 degrees or less, and wherein the through passage and an upper one of the discharge passages are coaxially connected to a main transportation pipe of the gas transportation pipe system for grain and a lower one of the discharge passages is connected to a branching pipe of the gas transportation pipe system for grain. It is also appropriate that the shape of the inside diameter of the introducing passage in the output side part thereof, which is gradually decreasing in size toward the downstream side, is a slope. It is also appropriate that an angle of the slope is 30 degrees or less. It is also appropriate that the shape of the inside diameter of each of the pair of the discharge passages in the input side part thereof, which is increasing in size toward the upstream side, is in an arc shape.